Thermostat housing, elbow and sensor

[86 1/2 Brutus]

All of the items came in for us to finish up Brutus's cooling system.  All that is left is the thermostat housing, thermostat, heater hose elbow and sensor.   I have a question though.   The elbow, the sensor, and there is a what looks like a set screw on the housing.  Do i put rtv on these threads?  teflon tape? or nothing?

[ArdWrknTrk]

I like anerobic 'Pipe Sealant with Teflon' (PST)
There's no stringy tape to possibly come free.  (this is much more important in an oil gallery than a coolant system)

There's no chance that you don't get a metal to metal ground for your sensor.
And there's no chance of mistakenly using **acetioxy** chemistry that is going to corrode the brass sensor over time, creating a resistance that gets higher in the long term.

And, if your thermostat doesn't have a little jiggly brass nub in the flange, I'd suggest drilling a miniscule hole so air can escape as you're filling the system.
It will never be enough to really affect the function of the thermostat, but it will ensure a thermostat will always be submerged it the coolant it's meant to regulate.

[Gary Lewis]

I second Jim's recommendations.  I'm using Loctite 56747 PST 50ml High Temperature Thread Sealant for Stainless Steel Fittings.  It is expensive, but really works.  I've had no leaks and no seizing of the bolts.  

And, I drilled a small hole in my thermostat.  But, maybe mine wasn't big enough as it didn't seem to help with the initial fill as I still had some air in the system.  However, it sure didn't hurt.

[ArdWrknTrk]

Gary,
I'm not sure of where the radiator cap is in relation to the thermostat housing on a 300.

I know on our trucks it still takes some circulation to purge the heater core and upper radiator hose once you button the water neck back up.

But all the V-8's have a bypass, where I think the water pump is dead headed in a 300.

[Gary Lewis]

You are right, the only bypass on the 300 is through the heater core.  

[85lebaront2]

Gary, Jim, there is an internal bypass on the 300, it is a hole in the block that connects the front of the head to the water pump where the heater return hose goes in. I thought I remembered one being there from working on a few of them. Due to it's location, much like the V8s, it doesn't really help purging the system. The "setscrew" on the thermostat housing might be a bleeder screw to aid in purging.

[Gary Lewis]

I wasn't aware of that, Bill.  Thanks!

[86 1/2 Brutus]

The set screw is for purging if i remember correctly.    I think i'm going to take Jim and Gary's advice and order the high temp sealant, i checked at autozone and they dont have any.  I can get some from amazon in a few days.